Optimal extent of left recurrent laryngeal nerve para-lymph node dissection in esophageal squamous cell carcinoma: a retrospective analysis based on cytokeratin 19 immunopositivity for micrometastasis detection.

No consensus has been achieved for the optimal extent of left recurrent laryngeal nerve para-lymph node dissection (LRLN-LND) for esophageal squamous cell carcinoma (ESCC). Surgeons follow different extents according to their experience, technical proficiency, and habits. Immunohistochemical (IHC) analysis is a feasible method to detect micrometastasis (MM) of lymph nodes in ESCC. We hereby explored the optimal extent of LRLN-LND by detecting the routine pathological and MM-positive rates of lymph nodes in different regions. We retrospectively reviewed patients who underwent R0 resection and LRLN-LND between September 2018 and July 2019. We divided lymph nodes into four groups based on the LRLN and cervicothoracic junction plane: (i) anterior LRLN region above the plane, (ii) posterior LRLN region above the plane, (iii) anterior LRLN region under the plane, and (iv) posterior LRLN region the plane. In total, 263 lymph nodes were collected from 52 patients. We detected MM based on cytokeratin 19 (CK19) immunopositivity in lymph nodes with negative histological detection. We calculated the positive rates of routine pathological and MM detection and analyzed the metastasis status in different regions. Lymph nodes of cervical regions (group 1 and group 2), which are always ignored due to inherent technical difficulties and poor exposure, showed higher positive rates than those in group 4; the rate in group 3 was also higher than that in group 4. Routine histological detection achieved positive rates of 8.9, 6.7, 1.6, and 0.9%, respectively. After the detection of MM by the CK19 IHC method, increased positive rates were achieved. To the best of our knowledge, only a few studies have focused on the optimal extent of LRLN-LND. Because of the high positive rates both in routine pathological detection and by CK19 IHC MM detection in this study, thorough LRLN-LND during esophagectomy for ESCC is necessary, including the cervical region and anterior nerve region adjacent to the trachea.